Resistance amplifier



Sept. 29, 1925; 1,555,037

J. S. STONE RESISTANCE AMPLIFIER Filed Oct. 4, 1921 INVENTOR.

Jab/g ftowe Jfane ATTORNEY Patented Sept. 29, 1925.

curred STATES PATENT oi-Pica.

JOHN STONE STONE, OF SAN DIEGO, CALIFORNIA, ASSIGNOR TO AMERICAN TELE- PHONE AND TELEGBAPHQOMPANY, A CORPORATION OF NEW YORK.

RESISTANCE AMPLIFIER.

a licationfiled October 4, 1921. Serlalin. 505,351.

To all whom it may concern: v I

Be it known that 1, J HN STONE Sronrz,

San Diego and State of California, have in- 5 vented certain Improvements in Resistance Amplifiers, of which the following is a specification. This invention relates to methods and means for amplifying resistances, and in particular is adapted for use in cases where a telephone transmitter of the microphone type is to be used in a circuit 'in'which the apparent resistance of the transmitter,-

or the lmpedance which it ofiers in the circuit, should be larger than the actual ohmic resistance of thetransmitter. That is, the

invention is a method and means "for magnifying or amplifying afresistance.

It occurs in certain circuits, such as high frequency circuits, that the impedances in volved are quitejhigh and in case any apparatus, such as a telephone transmitter or a telephone receiver, is to be used therein,

high efiiciency requires that the impedance 1 ofl'ered by said apparatus be of about the same magnitude as the remainder of the circuit with which it is associated. 'In general, however, the resistance of a telephone I transmitter is quite low and is not, therefore, well adaptedfor use in such circuits.

Heretofore it has been common to increase the apparent resistance of the transmitter or receiver or other element by placing it in the secondary of a step-down transat former, but the transformers are never perfeet and ofier a certain leakage reactance, depending upon the frequencyof the oscillations in the circuit. .This leakage reactance can, in art at least, be neutralized by 40 a series con enser in the primary or the secondary of the transformer, but since the leakage reactance is itself a function of the resistance of the element, such neutralization can .never be completely effective, and the rimary circuit of the transformer-cannot be maintained 'inresonance for a given frequency when the resistance is varied, as

is the case-Where the resistance is a telephone transmitter. I residing at San Diego, injthe county of Y My invention will be better understood by reference to the accompanying drawing, 1 taken in connection with the specification. In this drawing, Figurel is a. eneralized circuit showing connections whic will give the desired results, and Figs. 2, 3 and 4 are specific forms of circuits.

In case the resistance element is a microphone transmitter of resistance R or conductance 9 an increase of pressure on the diaphragm results in a decrease of resistance or an increase of conductance, and for small changes, theincrease in conductance is approximately proportional to the increase 1n pre ssure, so that its conductance at any pressure-is given loy where g, is the conductance at unit pressure. a and p is the instantaneous value of the pressure. 'In case the pressure on the diaphragm is varied in accordance with a sine function, there will he the relation =yotro+rr 8111 v An analytical consideration ofthe circuit of Fig. 1 will be of assistance in understanding the invention, in which figure R is a resistance such as a telephone transmitte'r, and X is areactance in series with R, while X is a reactance in shunt to R and X,. In the case of the circuit of Fig. '1, Fig. 2 and Fig. 3, the admittance y as viewed from outside the loop circuit, will be given by a l 1- L 7' m 1. Therefore where R, 1 jten a? ei m If be made large compared to unity, 3; becomes sensibly a pure conductance where R is the apparent resistance of the transmitter. From this last equat on it is seen that under theimposed' condit ons of s X X a and mgor R If 2 2- is small compared to unity i Sin wt 3 I 1 I goPo Z90 rigis not sufiiciently small the higher o power terms in equation 2)]will cause distortion. This may be re need by the suitable use of-resistance and part of my in vention consists in such use. in' Fig. 4, where a reistance R of conductance g is connected in shunt to R. In

such case the quantity gin equation (2')? is to be replaced by (y -kg) and it b e 1 1 a g 7 (9-+9) v8*(9.+yoza+ tg ,si at If now g. is made sufficiently large so that is small compared to unity, equation (4) becomes at) a mission is obtained.

From theforegoing it will be seen that by placing the transmitter ,or other resistance element in a resonant loop circuit the apparent resistance of the element will be magnified by the factor (1-1-3 9 .and

v thzitdistortion may be diminished by placing a second resistance in shunt to the resistance 'to be magnified'; .It will further 'be seen that placing a resistance shuntabout a telephone transmitter will improve the iglmlity ofitheftransniission whether Or not e transmitter be P placed the l resonant ,l0op-circuit,"'andthat when" it is so placed in a resonant loop circuit the; greater the This is shown and thus substantially distortionless' trans-:

1 seats? large compared to unity the resistance of the-transmitter has been multiplied by a I 3 1 We Inthe case of Fig. 2, X =Lwand X while in case of Fig 3, X13060 and X =Lw whence in either case s U The condition X -X is realized by mail-- ingLCcFzl. When therefore sg is large compared to unity and CLQEL amplification the there be. i

What is claimed is! 1. The methodof reducingthe distortion in a telephone transmitter which consists in connecting a resistance in shunt to said transmitter. j

2. A circuit adapted to carry an alternatiess distortion Will ing current and containing a resistance ele- 1 comprising a resonant loop circuit in which 1 tively large, the resistance element being connected in series in one, side of said loop circuit, and a second resistance connected in complete circuit has an increased resistance atthe desired 'frequency and is i,.s ubstantially w free from distortion with variation of the resistance of said element;

1 4. In combinationin a network, a

I v resist- "ance ofvariable value, akshunt reslstance associated therewith and offconstant magm 'the ratio ofinductance to capacity, is relashuntto said resistance elementrwhe'reby the tudeconsiderably greater than any value attained by the saidvariable resistance, and means comprising reactance elementsto increase the resistance of the network considerably above that of the said two resistances in, parallel.

5. In combination, a telephone transmitter, a reacta'nce in series therewith, anoppo site reactance ,in parallel withsa'id series combination and .a relatively large constant resistancev shunting" the said" transmitter whereby the resistance of the combination is increased overthatfof the said transmitter and is more constant than that of the said transmitter.

6. In combination, a variable resistance and a shunt resistance of substantially 5 greater magnitude and constant value, a reactance in series to said resistances in parallel and an opposite reactance in parallel with the entire foregoing combination whereby theresistance of the entire combination is greater than of said variable 1 resistance and more nearly constant.

In testimony whereof, I have signed my name to this specification this 26th day of September, 1921 JOHN STONE STONE. 

